Our Second Second Rocket Mass Heater

We finally decided to go ahead and rebuild our second rocket stove (the one in the living room). My primary wishes were to rebuild the core (better) and to convert the relatively useless mass into a (small) bench. Iulia decided to make it a workshop and …  3 interested people showed up.

During the first day we settled into being together. I left the existing rocket mass heater in tact so we could review its shortcomings together and learn from that. We talked about the basic workings of a rocket stove while talking about the existing stove.

… and then we took it apart:

We had only one wheel barrow of waste which was non-toxic and we dumped it as back-filling at the earthbag cellar.

Though there was some soot in the rocket (sometimes it didn’t burn completely clean) there was very little of it given that it worked for 6 winters. There was a 1cm layer of light and fluffy ash sitting at the top of the heat riser (accumulated over the same period of time).

Until we reached the brick platform upon which the rocket was built.

We then layed out the expansion of platform for the new rocket.

… and started building it … giving everyone their first experience at working with mortar and laying bricks.

The next morning we finished it!

With the platform done we built a mockup of the core (while learning about dimensions and sizing using standard brick sizes) and its place on the platform (and relationship to the bench).

We then settled into a rhythm in which two people were laying bricks (one working on the core, the other working on the bench) and two others were preparing soil for mortar and cob (and doing other support tasks such as cleaning bricks so that the brick layers could work smoothly).

As the chamber that is under the bench started to take for, I figured out how we were going to close the top of the chamber  (close from the chamber that makes the bench. The plan I came up with involved recycling two concrete slabs we had lying around together with some bricks. Next I had to figure out how to create a structure that could support that top while allowing a good flow of gasses through the chamber itself. It was a bit of a puzzle but we solved it.

… and the core was rising up

… and the chamber was rising up … and we were starting to apply cob (especially on the back side where access would become more difficult as the construction grew):

… and I think this is where we finished up on day 2:

On day 3 as most of the riddles were behind us and everyone had a better sense of the materials and the work, progressed flowed and accelerated. The core was completed and the chamber layout finalized. While the chamber was being closed up the heat riser was growing.

Pretty soon we were insulating the core with  perlite in a clay slip (recycled from the previous rocket) in the chamber built around the core:

… and then the insulation sleeve around the riser was put in place (recycled from the previous rocket) … and also filled with perlite:

… and finally the barrel came on (for the last time – we had quite a few fittings), we sealed all around it with cob … and lit the stove … and despite adverse conditions (a new rocket filled with moisture, on a warm summer day) we all smiled when we saw the flames getting sucked into the rocket and the dragon came to life. Very soon we were in an overheated room with a warm bench (that nobody wanted to sit on).

… in the excitement (and a bit of rush to accommodate the schedule of one of the participants) I missed taking a picture of the barrel on the “raw” rocket … but the next day (today!), with Liam’s help preparing soil and mixing cob, we were able to get much of the cob work done (and we may complete the rough structure tomorrow).

Even though it is using the same floor area as the previous rocket, the footprint of the new build is much larger … and it dwarfs the room … which feels a bit off. That is a price we’ve paid for having a warm bench to sit on (without taking on a much larger renovation).

It was an intense weekend. I’m glad to have had an opportunity to share rocket stoves with Tudor (missing from the picture below because he had to leave before we took it) , Dan and Liam and Iulia. I’m glad to have a good core with hopefully a comfortable bench for next winter.

One Reply to “Our Second Second Rocket Mass Heater”

  1. Wonderful!!! I always wondered, and now its more satisfying to at least understand, but really, one needs to get their hands messy to really get it! Thanks!!

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